This soft anti-slip material is used under saddlebags and/or non-magnetic tankbags to protect the paintwork of the motorcycle against damage or scratches. It can also be used in combination with magnetic tankbags, provided that the magnets are powerful enough. Oh yes, the trick with the tape dates from the time when this kind of paint protection didn't exist. This is a lot more efficient, more convenient and less sticky.
Although most bags are also equipped by default to make an effort in that respect, you should not underestimate the impact of a (highway) ride on elements that have been externally attached. Weather and wind, weather conditions, speed, even a minimal amount of slack can cause bags to move or shift while on the road. With a size of 60 cm by 90 cm you can already protect some paint and play it safe. Discovering that your bike has some new scars after a nice trip, is not fun at all.
Attention!
Although with powerful magnets it is possible to use this paint protection system safely, a little caution is advised. Again: do not underestimate a motorway trip. The principle is simple: as soon as the forces acting on your motorcycle (speed, wind...) are greater than the forces keeping your magnets (with a layer of lacquer protection) on your tank, your tankbag will disappear as fast as it can. With all the consequences this entails.